Johansson B, Rydqvist B
Acta Physiol Scand. 1983 Feb;117(2):183-94. doi: 10.1111/j.1748-1716.1983.tb07196.x.
Isolated slowly adapting stretch receptors of the crayfish (Astacus fluviatilis) were exposed to sinusoidal length changes. The mechanical force, the receptor current and the receptor potential were analysed in terms of frequency response (Bode plots) and input/output functions. Within the frequency range investigated (0.3 to 80 Hz) the mechanical force was found to be only slightly dependent on the frequency of the sinusoidal stimuli, the slope of the gain function in the Bode plot being close to zero. Dynamic length-force curves exhibited a characteristic hysteresis. In potential clamp experiments, the receptor current induced by sinusoidal length changes was dependent on the clamp potential attaining maximal amplitude at a membrane potential of about -20 to -30 mV for 80 Hz mechanical stimulation. The membrane potential at which the receptor current changed sign (the reversal potential) increased with increasing frequency. In Bode plots of the receptor current the gain was represented by a straight line, having a slope of about 1.2 dB/octave. The phase shift was positive at low frequencies. Bode plots of the receptor potential gain exhibited a characteristic peak in the region of 15 Hz. Below this peak the gain increased with about 1.2 dB/oct, above the peak the gain decreased with about 4.8 dB/oct. There was a small positive phase shift at low frequencies; at high frequencies the phase shift became negative. The impedance of the cell, as calculated from the receptor potentials and the current responses at resting membrane potential, gave Bode plots comparable to a simple resistive-capacitive filter compatible with the electrical properties of the receptor cell membrane. The cut-off frequency of this low pass filter decreased with decreasing stretch amplitude. One physiological significance of this finding, is that the performance of the receptor is improved at low levels of stimulation by reducing the bandwidth of the system.
将小龙虾（Astacus fluviatilis）的孤立慢适应性牵张感受器暴露于正弦长度变化中。从频率响应（波特图）和输入/输出函数方面分析了机械力、感受器电流和感受器电位。在所研究的频率范围内（0.3至80赫兹），发现机械力仅略微依赖于正弦刺激的频率，波特图中增益函数的斜率接近于零。动态长度-力曲线呈现出特征性滞后现象。在电压钳实验中，正弦长度变化诱导的感受器电流取决于钳制电位，在80赫兹机械刺激下，在约-20至-30毫伏的膜电位时达到最大幅度。感受器电流改变符号时的膜电位（反转电位）随频率增加而升高。在感受器电流的波特图中，增益由一条直线表示，斜率约为1.2分贝/倍频程。低频时相移为正。感受器电位增益的波特图在15赫兹区域呈现出一个特征峰。在该峰以下，增益以约1.2分贝/倍频程增加，在峰以上，增益以约4.8分贝/倍频程下降。低频时有一个小的正相移；高频时相移变为负。根据静息膜电位下的感受器电位和电流响应计算出的细胞阻抗，其波特图与与感受器细胞膜电特性兼容的简单电阻-电容滤波器相当。该低通滤波器的截止频率随拉伸幅度减小而降低。这一发现的一个生理意义是，通过降低系统带宽，感受器在低水平刺激下的性能得到改善。
